In general, casters are mounted on the bottom of machinery equipment in a variety of industrial fields as well as pianos, chairs or mobile beds for accommodating and transferring patients used in hospitals, carts for transporting goods and carts with which people work, to thereby allow people to easily transport heavy goods or products or machinery.
In addition, a stopper or brake is provided at casters that are roller wheels, respectively, in order to prevent the roller wheels from rolling. This stopper is not provided at respective front and rear legs of the above-described various kinds of wheeled products, but is provided only at the respective front legs or the respective rear legs at most. This is because the wheeled products can be stopped even if only the wheels provided at the front or rear caster are prevented from rolling.
The casters equipped with stoppers or brakes are more expensive than those having no stoppers or brakes. Accordingly, makers that produce the above-described various kinds of wheeled products do not produce wheeled products at all the front and rear legs of which expensive controlled casters are provided, but produce wheeled products at all the front and rear legs of which two types of controlled and uncontrolled casters are provided in combination.
In addition, service lives of casters may become longer or shorter depending on quality of bearings rotatably supporting yoke frames, respectively. For example, if a bearing is of poor quality, a service life of a caster is shorter, but if a bearing is of good quality, a service life of a caster is longer. Thus, manufacturers producing wheeled products such as pianos, chairs, and mobile beds produce wheeled products using casters with bearings whose lives are long.
Most of conventional controlled casters are respectively configured to have a structure that stoppers or brakes are assembled in advance on caster shafts that are rotatably assembled with yoke frames, respectively. Accordingly, the controlled casters with stoppers or brakes should be designed to correspond to yoke frames larger than those of the uncontrolled casters having no stoppers or brakes, because the yoke frames should be able to accommodate the stoppers or brakes.
In addition, since controlled and uncontrolled casters differ from each other in view of specifications of yoke frames, as well as in their structures, these casters cannot help being separately produced through respectively different manufacturing processes.
As described above, since uncontrolled and controlled casters differ from each other in view of their specifications and structures, manufacturers producing wheeled products such as pianos, chairs, and mobile beds should design a structure of legs of the wheeled products in various forms depending on their specifications and structures of the casters with and without having no stoppers or brakes, to thus increase a cost of designing the wheeled products. In addition, uncontrolled and controlled casters should be accurately selected and assembled when the above-described wheeled products are produced, which makes an assembly process of the wheeled products tricky and thus lower a productivity.
Meanwhile, in the case that bearings used for controlled casters are of poor quality but those used for uncontrolled casters are of good quality, manufacturers producing wheeled products may have problems that controlled casters cannot be substituted with uncontrolled casters for legs assembled with the controlled casters and vice versa. Thus, stopper that are assembled with uncontrolled casters, that is, brackets of roller wheels to thus control the roller wheels have been recently being proposed.
As an example, caster stoppers was disclosed in Korean Patent Laid-open Publication No. 10-2005-0006728, entitled “a caster stopper.” In this Korean Patent Laid-open Publication No. 10-2005-0006728, a caster includes a yoke frame that is assembled with a bearing support portion and an attachment bolt attached to each leg of various kinds of wheeled products such as pianos, chairs, mobile beds and carts, and a wheel assembled to the yoke frame in a freely rotatable state, and a caster stopper includes a fixing unit and an operating unit. In the fixing unit, the top surface and the right/left surfaces that are attached to each other in a modular type are integrally formed at one side of the yoke frame, so as to surround the opposite outer surface of the bearing support portion. An elastic braking piece that is slantedly protruded downwards toward the rear side to elastically brake the wheel, is formed at the rear end of the top surface of the fixing unit. In the fixing unit, side brackets that are protruded in parallel toward the rear side are integrally formed at the rear ends of the right and left surfaces of the fixing unit. A bearing portion elastically pushes the elastic braking piece, in a state of being assembled rotatably by a shaft pin having both ends fixed to the side brackets. A push plate is integrally formed in the operating unit.
Thus, if the push plate is pressed and attached on the surface of the roller wheel, the rolling operation of the roller wheel is stopped.
However, since the rolling operation of the roller wheel is stopped by the push plate that has been attached on the surface of the roller wheel, in the case of the conventional art, an actual braking force is not large. As a result, the roller wheel happens to roll although the push plate has been pressed to perform a braking action. In addition, since an adhesion force between the push plate and the surface of the roller wheel falls down significantly, in the case that various surrounding dirts are adhered on the surface of the roller wheel or the surface of the wheel is wet at the time of raining, depending on conditions of work sites, the braking force created by the push plate drops significantly. Further, if heavy stuff is loaded on or unloaded from the wheeled products on a slope road, a danger may be caused.